Simon Marlow, a developer in microsoft research Cambridge, has agreat tool to download Visual Haskell
Just download and install it, then you can develop haskell program in vs.net editor, also they have good features like tootip etc..
we need that because haskell is really hardly understand with their syntax...
Also you better look at this paper, which discusses in detail how this completed and how the vs.net plugin working..
There is a screen shot on the site.